The present invention refers to a sprinkler device for fire extinguishing systems. These sprayer devices, also known with the English term xe2x80x9csprinklerxe2x80x9d, are usually coupled to a supply line of a pressurized fluid or liquid, typically water, and placed above a predetermined area to be protected against possible damages caused by a fire.
Usually the sprinkler device comprises a body made from metal material having an inlet duct and an outlet duct between which a path is delimited for the liquid; the inlet duct is apt to be coupled with the above fluid supply line, whereas a diffuser means integral with the body of the sprinkler device is usually located below the outlet duct, which is apt to sprinkle the liquid with a rainjet over the area to be protected.
A shutter is arranged upstream or in correspondence with the outlet duct which, under normal conditions (i.e. in the absence of a fire) hinders the fluid outflow from the sprinkler device. Moreover, room temperature sensing means are associated with the body of the sprinkler device, which are usually directly exposed to the area to be protected; when a predetermined temperature threshold (indicative of a fire) is exceeded, such means cause the shutter to move, so as to let the liquid flow through the outlet duct towards the diffuser underneath, which will then sprinkle the area to be protected.
As it can be seen, the above devices are apt to cause the automatic opening of the liquid supply line, in order to obtain the flames extinction, should the room temperature increase to an extent deemed to be excessive; accordingly, it is also clear that the sprinkler devices need to have means for sensing the temperature of the room where they operate, and be able to fastly switch when a predetermined temperature threshold is exceeded.
The room temperature sensing means, which as said are also provided for enabling the fluid outflowing from the sprinkler device, may be of various types.
Usually, such means consist of a tightly sealed container, such as a glass bulb, containing a material which expand as a function of the temperature of same container; in the instance of a fire, the volume increase of the expansible material, due to a temperature increase of the container, will cause the latter to break out.
According to this solution, the container is placed in the sprinkler body to keep a shutter plug in closure of the liquid outlet duct, somewhat like a prop or supporting column; the cracking of the container, caused by the too high room temperature, deprives the plug of its support, which is expelled from the sprinkler body under the pressure of the fluid available in the path, thus releasing the fluid flow.
In other known solutions, instead of a glass bulb, sensing elements are provided, which are made from alloys melting at predefined temperatures; in such instances a mechanical kinematic motion is usually provided, which has two portions in a precarious welded to each with a melting alloy, so as to obtain a stable supporting column for the shutter plug; following the melting of the alloy, due to the room temperature being too high, the kinematic motion is released in the sense that the two portions may get free from each other, thus releasing the shutter plug and opening the liquid outlet duct.
Though the above solutions are accurate and reliable on an average, they have the drawback of using room temperature means of the disposable type, i.e. which become fully unusable after their first operation, with a consequent need of having to provide for their replacement.
Another associated drawback is that the sprinkler devices using the above room temperature sensing means are unable to provide for the automatic resetting of the closed condition of the fluid supply duct, and therefore to stop the fluid supply also when the fire has ceased, with a consequent damages risk due to water flooding.
Other known sprinklers have room temperature sensing means which on the contrary actuate a shutter capable of motion from a closed position to an open position of the liquid path; such sprinklers are actuated for their opening by the room temperature increase and back, for then returning to their initial closed condition, as soon as the reasons for operation have ceased, thus avoiding possible damages from flooding.
However, such known solutions have the drawback of using a bimetal as a sensing and actuator means, which has a weak force (in the order of a few grams) and a restricted stroke (a few tens of millimeter for small bimetals or anyway a few millimeters for large bimetals, i.e. in the order of a few tens of millimeter) and is not apt to actuate the shutter of the sprinkler device directly; in these instances, the sprinkler device has to be equipped with a complex servo-hydraulic circuit for changing the small bimetal motion in an ample movement of the shutter, whose force is capable of winning the fluid pressure.
Other known sprinkler devices provide the use of a motor-driven shutter; in such instances a special electric or electronic control thermostat has to be provided, which is apt to sense room temperature and electrically supply the motor for causing the shutter motion and consequently the opening of the liquid outlet duct, if required.
However, also these solutions have some drawbacks, in particular due to their dimensions, manufacturing difficulties and cost.
The present invention has the aim of solving the above drawbacks and providing a sprinkler device for fire extinguishing systems which has an improved structure with respect to the known state of the art.
Within this frame, an object of the present invention is to provide a sprinkler device having room temperature sensing means, which do not require to be replaced after their first operation, and which are reliable and efficient with time, have restricted dimensions and a low cost.
Another object of the present invention is to provide such a sprinkler device which allows for an automatic resetting of the closed condition of the fluid supply duct, after the fire has ceased.
These and other objects, as better described in the following, are obtained according to the present invention by a sprinkler device for fire extinguishing systems, having the features of the annexed claims, which form an integral part of the present description.